Mix the garlic, pepper and salt together. Coat the top of the prime rib evenly (under fat cap), before acclimating to room temperature, about 3 hours. Preheat oven to 350 degrees. Place beef roast (fat side up) on a rack in an open roasting pan to catch juices. Roast in oven until meat thermometer reads five degrees below desired doneness (135 degrees for rare, 140 degrees for medium rare, 155 degrees for medium). Allow roast to stand for 15 to 20 minutes before slicing. During standing time, the temperature will continue to rise and reach the desired doneness. ** The ribs on the roast should be removed and tied back on by the butcher.